December's Lunar Occultations: Uranus and Mars

During the month of December our Moon passes close to the planets Jupiter, Uranus and Mars making such close encountersnic e photographic opportunities. However, the nights of 5th December and the morning on 8th December should be put into your astronomical diary as these dates mark the times when the Moon passes in front of the planets Uranus and Mars respectively. The moon during the course of its orbit around the Earth passes in front of many stars, mostly faint, so when the Moon obsures a planet is quite a rare event. When the Moon passes in front of a celestial object, this event is referred to as a Lunar occultation.

The information given below refers to the location of Munich and the times are local (UTC+1), and the event visibility and timing will depend on your location.

Lunar occultation of Uranus: Evening of December 5th

Uranus position relative to the Moon near the start (left) and end (right) of the event.

About an hour after sunset the ~94% illuminated waxing gibbous Moon will be in the twlight eastern sky shining at ~-12th magnitude. Near the slim unilluminated northwestern limb will be the planet Uranus which, lying at near ~19 AU from the Earth, will be at magnitude ~5.9 and have an apparent size of just ~3.8 arcseconds so will appear in a telescope, even at high magnification, as just a very small blue-green disc.

Just after 1733 hrs local time, the Moon will begin to pass in front Uranus, taking just approximately ~12 seconds to cover the small disk of the planet, not far from the Lunar region Bay of Dew. Just under an hour later, when the sky will be darker, Uranus will reappear on the illuminated side of the Moons limb near the ~550km lunar crater Mare Crisium. This occultation event will be visible from northern Asia, Russia, Africa and most of middle and eastern Europe.

The image (left) is a simulation (using Stellarium) that shows the proximity of Uranus to our Moon just before the occultation starts (left) and ends (right) through a Celestron 8" aperture SCT (or 8" EdgeHD) telescope which is a popular sized instrument for amateur astronomy for Lunar, planetary and deep sky observing and imaging with a Baader 24mm Hyperion 68° Eyepiece - Non Variable (#2454624 , € 165) . This particular configuration would allow the Moon and Uranus to appear in the same field of view for viewing the disappearance and reappearance of Uranus.

Other eyepieces of course can be used to view this and the occultation of Mars (as well as just for Lunar and planetary observing) including our Classic Ortho/Plossl and Morpheus range. At the moment, until December 31st, our Hyperion range are on a Holiday special with 20% off pricing with the fixed focal length 5mm to 36mm models, 8-24mm MK IV Zoom (with and without 2.25x barlow) and the Starter and Complete eyepiece set with case all being included in this offer. You can read more about our current eyepiece range, their features and usage in our recent article "The eyepiece series from Baader Planetarium"

Lunar occulation of Mars: Morning of December 8th

The setting Moon and Mars - a simulated view using Stellarium with an 8" SCT and Hyperion 24mm

Mars will be at its closest approach to Earth on December 1st lying just over 81 million kilometres distant and will have an apparent diameter of 17.2 arcseconds. A week later it will be at opposition on the 8th December where its apparent size will be just slightly smaller at 17.1 arcseconds. This latter date also marks the time that our Moon will pass in front the planet too - a rare event. During the evening of December 7th, Mars and the Moon will be bright "near neighbours" in the sky with the Moon shining at ~-12.5 and Mars at ~-1.9. As the evening moves into morning of the 8th, both objects will get closer and closer. If you want to see this rare occulation of Mars you will have to stay up all night (or go to bed and put your alarm on) until not long before sunrise. The event will be visible from mny parts of Europe and northern Europe, northern Africa, Greeland and north America/Canada.

Moon and Mars before the start of the occultation. Simulated view through an 8" SCT with a Baader Hyperion 5mm eyepiece.

Just before 06h06m local time the setting full Moon, which will be only around 18 degress in altitude towards the WNW direction, will start to move infront of the planet and just over ~30 seconds later Mars will be hidden from view. Just under an hour later just after 07h01m the red planet will peek over the Moon's eastern limb again taking ~30 seconds to become fully visible once again. By this time the Moon and Mars will only be around +10 degrees in altitude with a brighter pre-dawn sky.

The image (right)  shows a simulation (from Stellarium) near the start and at the end of the Lunar occultation of Mars using the same 8" telescope and Hyperion eyepiece configuration as mentioned earlier.

The image to the left is a simulation that shows a more magnified view just before the start of the occultation using the same telescope but with a Baader 5mm Hyperion 68° Modular Eyepiece (#2454605 , € 165) giving a magnification of just over 400x.

Imaging the occultation

Celestron's NexYZ smartphone adaptor (smartphone not included)

There are many ways of recording the occultation of Uranus and Mars events and will depend on what equipment you have to hand.

A simple set up without a telescope would be to use short exposures with a DSLR/mirrorless camera and a telephoto lens. A good sturdy tripod would be needed to support and keep the camera-lens configuration steady. Our Astro & Nature Photo Tripod w. Fluid Head and quick mounting plate (#2451020 , € 235) is a good choice as it can accommodate ~3kg of payload and features a fluid head for smooth camera movement while keeping track of the motion of the Moon across the sky.

Afocal projection imaging is one method to "get up close" to the celestial action and can be used with smartphone camera and compact cameras. If you have a compact camera, you can position it close to the eyepiece but positioning the lens to the eyepiece, and then holding the device steady while trying to take the photo is quite difficult. To keep the camera steady and correctly aligned and positioned with the eyepiece, the Microstage II Digiscoping Adapter (#2450330 , € 55) is an inexpensive but simple, sturdy and effective accessory.

An example of eyepiece projection imaging with a DSLR using a Hyperion 8-24mm MK IV Zoom eyepiece

Celestron's NexYZ 3-axis adaptor clamps to an eyepiece and allows you to attach a smartphone with simple easy-to-make adjustments of the smartphone's camera lens relative to the telescope eyepiece lens to get that "perfect shot".

You can also couple a DSLR camera without a lens, or a dedicated Lunar/planetary imaging device, to an eyepiece for doing eyepiece projection photography. The Hyperion (and Morpheus) eyepiece range make this type of photography simple with a range of adaptors. The image (left) shows a DSLR coupled to a Baader Hyperion Universal Zoom Mark IV, 8-24mm eyepiece (1¼" / 2") (#2454826 , € 275) .

Simulation of the appearance of Mars through an 8" SCT using a QHY 462C planetary camera. The approximate field of view is the outer red-line box.

A dedicated lunar/planetary imager attached to a telescope will allow you to capture Uranus' and Mars' disappearance and reappearance from behind the Moon at high frame rate. For example the QHY 5-III-462C CMOS Camera (#1931026 , € 375) , with its small 2.9 micron pixels, high sensitivity and low noise can record at up to 135 frames per second and is currently on offer. More planetary imaging/guiding cameras can be found here.

You can find more information about different imaging methods in our recent blog "The camera at the eyepiece", and also in our Digiscoping guide which covers the use of smartphones, compact cameras, DSLR/mirrorless and planetary imaging cameras and what adaptations are needed to connect them to a telescope/eyepiece for afocal and eyepiece projection photography.

We would love to see your images of these rare occultations so please do send them in!

We all wish you clear skies and happy observing/imaging for these upcoming events!

About the author

Lee Sproats

Dr. Lee Sproats has been interested in astronomy since watching Star Wars in 1977 and has appeared on the UK Sky at Night TV programme. He then went on to study Astronomy where he obtained a degree and then a PhD in the subject at University College London/Mullard Space Science Laboratory. He has worked in Australia in radio astronomy and used optical/infrared telescopes on Hawaii and La Palma and Lowell and Kitt Peak observatories in the USA. After working for the University of Surrey to promote the use of computers for teaching in UK higher education and then as an IT trainer for a stock market company, he went on to work for Greenwich Observatory Ltd where he ran their northern branch and then worked for David Hinds Ltd dealing with our and Celestron products. He is often involved in flight excursions that take passengers to observe the northern lights, has led trips to see the great USA 2017 eclipse near Hopkinsville and was lead astronomer onboard a specially chartered 737 to view the 2015 total solar eclipse at 38,000ft. Lee`s astronomical interests include Lunar observing, astrophotography, photometry and pro-am collaborations.

Since David Hinds stopped operation in December 2020, Dr. Sproats works for Baader Planetarium as our UK representative/consultant and is responsible for looking after our UK/Eire dealers, dealing with Baader Planetarium/PlaneWave/10Micron product support, writing articles and also is involved in our large telescope and observatory instrumentation projects.

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